Portable electronic devices such as a cellular phone and a PDA including a liquid crystal display device, an organic electroluminescent display device, and the like, now need a further reduction in its size and weight. Along with this, downsize of a periphery of a display region, i.e., a reduction in area of a frame region is needed, and a technology of satisfying such a need is now being researched and developed. In addition, in view of the reduction in thickness and costs, and the like, a display device including a full-monolithic circuit board where a peripheral circuit needed for driving a driver circuit and the like is arranged on a substrate is increasingly employed. According to such a full-monolithic circuit board-including display device, a circuit for driving pixels is arranged on a circuit board, which increases a region (frame region) except for a display region of the board. So a reduction in frame region of such a device is being researched and developed.
In a conventional display device, a wiring that is formed inside a panel is made of aluminum and this wiring is extended to the outside of the panel to be used as an external connection terminal. In such a case, the aluminum film might be corroded. In view of this, the aluminum film that is used as a wiring formed inside the panel is connected to a metal film that is arranged in a layer lower than the aluminum film, and this metal film is extended to the panel outside (for example, refer to Patent Document 1).
Patent Document 1 also discloses the following embodiment as an embodiment where corrosion of the external connection terminal is prevented. An aluminum film is used as a wiring formed inside the panel, and this film is extended to the outside of the panel and used as an external connection terminal. An end of the aluminum film, which is exposed to the outside of the panel, is covered with a chromium (Cr) film and an indium tin oxide (ITO) film, thereby preventing the corrosion of the external connection terminal.
[Patent Document 1]
Japanese Kokai Publication No. Hei-03-58019